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Habitat

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Rocky and soft bottoms. Most common around rocks. Often found half-buried in sand under rocks during the day; more active at night.
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Distribution

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Geographical Range: Alaska to San Diego
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Habitat

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Depth Range: Low intertidal to 90 m
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Comprehensive Description

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This cancer crab has a dark tip to the dactyl of the chela. The carapace is much wider than it is long, and its dorsal surface is nearly smooth and not covered with large bumps or tubercles. The propodus of the chela usually has several tubercles. The widest point of the carapace is at the 8th lateral tooth. Dorsal carapace is usually brick red, and up to 20 cm wide in males and 17 cm in females. The series of five points between the eyes are nearly equal in size and extend slightly farther out than does that of most cancer crabs, leading to the productus in the name. The dactyls of the walking legs have short setae. The carapace color pattern of juveniles is very different from that of adults, often white or with red and white stripes.
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Look Alikes

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How to Distinguish from Similar Species: The other large, common cancer crab species in the Rosario area is C. magister, which does not have a dark tip to the dactyl of the chela, and its carapace is widest at the 10th and last lateral tooth. C. antennarius has red spots on the underside of the carapace.Note: Species formerly in genus Cancer have been recently subdivided into several genera. Of our local genera, Cancer, Romaleon, and Metacarcinus have a carapace wider than long plus only scattered setae on the carapace margins and legs while Glebocarcinus has a carapace of approximately equal length and width, often with granular regions and with setae along the edges; and setae on the outer surface of the chela as well as on the legs. Metacarcinus can be distinguished from Cancer because Metacarcinus has anterolateral carapace teeth which are distinct and sharp plus the male has a rounded tip to the telson, while Cancer has anterolateral carapace teeth which are low and lobed, separated by deep fissures plus the male has a sharply pointed telson. Romaleon can be distinguished from Cancer and Metacarcinus because it has a distinct tooth on the anterior third of the posterolateral margin of the carapace while the other two genera do not.
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Invertebrates of the Salish Sea

Comprehensive Description

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Biology/Natural History: Predators include sand and kelp bass and sculpin and seabirds such as gulls and pigeon guillemots. Prey include barnacles and smaller crabs, amphipods, sea cucumbers, polychaetes, many other intertidal invertebrates, as well as dead fish. At least 42 prey species have been noted. Are an important threat to commercial oyster beds. Crabs raised on thick-shelled species such as Mytilus californianus developed even stronger claws. Mating occurs in summer after a female has molted. Males will often guard a female who is preparing to molt, by holding her under his abdomen. This may last for several weeks until she molts. He then guards her until her exoskeleton hardens again. Gravid females may be found from October to June. Females may carry from 172,000 to 597,000 eggs on the pleopods of the abdomen. Males overwinter in shallow areas, while females seem to overwinter in deeper water. Red rock crabs cannot osmoregulate and so are not found in areas of low salinity. Near Vancouver Island, adults have more epibionts than do juveniles. Common epibionts include barnacles on the dorsal surface, green, red, and brown algae, tube-dwelling polychaetes, hydrozoans, bryozoans on any region of the carapace. A few have sponge, tunicate, or mollusk epibionts. Dudas et al. found that the common local cancer crabs Metacarcinus magister and Cancer productus preferred the thin-shelled introduced varnish clam Nuttallia obscurata to the thicker-shelled clams Leukoma staminea and Venerupis philippinarum if access to all was equally easy. However, Nuttallia obscurata typically lives deeper in the sediment than do Leukoma staminea or Venerupis philippinarum. If they had to dig for them, Metacarcinus magister still ate more Nuttallia obscurata than it did of the other clam species, but C. productus' preference switched to Leukoma staminea and Venerupis philippinarum.
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Cancer productus

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Cancer productus, one of several species known as red rock crabs,[1] is a crab of the genus Cancer found on the western coast of North America. This species is commonly nicknamed the Pearl of the Pacific Northwest.

Description

Juveniles may be variously patterned

Cancer productus has carapace teeth that are somewhat broad and rounded with teeth between the eyes of nearly equal size and shape. The carapace of C. productus is widest at the posterior-most tooth, up to 20.0 cm wide. The pincers are large with distinctive black tips. This species lacks serrations or projections on the ventral side of the claws. Adults have a brick-red coloration throughout. The coloration of juveniles is diverse, often white, sometimes with red spots, or zebra-striped.[2]

Similar species

Dungeness crab (Metacarcinus magister) has serrations on the dorsal side of the chelipeds and lacks black tips. The graceful rock crab (Metacarcinus gracilis) has a single projection on the dorsal side of the chelipeds and also lacks black tips, and the widest point of carapace is at the second posterior-most tooth. The pygmy rock crab (Glebocarcinus oregonensis) has black-tipped chelipeds, but has large tubercles on the dorsum. Glebocarcinus oregonensis is also much smaller, such that a C. productus of similar size would generally have a striking juvenile coloration.[2] Cancer pagurus is very similar, but distinguished by its non-overlapping range.

Range and habitat

Closeup of a red rock crab

Cancer productus ranges from Kodiak Island, Alaska, to Isla San Martine, Baja California. It inhabits mid-intertidal waters to 79 m depth.[3]

Biology

Cancer productus is carnivorous; in Puget Sound it will crush barnacles with its large pincers for consumption. Small living crabs and dead fish are also eaten. Mating in this species occurs when the female is soft-shelled from October to June in Puget Sound. The male can often been seen guarding females until molting during this time.[4] This species is known to be a favorite prey item of the giant Pacific octopus, Enteroctopus dofleini.[5]

Fishery

Cancer productus is harvested by sport and commercial fishermen in California, mostly from Morro Bay south. The California rock crab fishery is made up of three species – the yellow rock crab (C. anthonyi), the brown rock crab (R. antennarium), and the red rock crab (C. productus). Rock crab landings for 1999 were 790,000 pounds and have averaged 1.2 million pounds per year from 1991–1999.[1]

It is not as sought after as Dungeness crab due to the considerably lower amount of flesh. However, the flesh has a delicate flavor and slightly sweet taste. The similar Cancer pagurus has a major commercial fishery in western Europe. Both males and females with a carapace exceeding 5 inches (130 mm) may be harvested in Washington, when in season.

References

  1. ^ a b Parker, David O. (December 2001). "Rock Crabs". Retrieved September 10, 2013.
  2. ^ a b Eugene N. Kozloff (1987). Marine Invertebrates of the Pacific Northwest. University of Washington Press, Seattle, WA. pp. 511 pp.
  3. ^ Gregory C. Jensen (1995). Pacific Coast Crabs and Shrimps. Sea Challengers, Monterey, CA. pp. 87 pp.
  4. ^ R. H. Morris, D. P. Abbot and E. C. Haderlie (1980). Intertidal Invertebrates of California. Stanford University Press, Stanford, CA. pp. 690 pp.
  5. ^ E. B. Hartwick, L. Tulloch and S. MacDonald (1981). "Feeding and growth of Octopus dofleini". The Veliger. 24 (2): 129–138.

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Cancer productus: Brief Summary

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Cancer productus, one of several species known as red rock crabs, is a crab of the genus Cancer found on the western coast of North America. This species is commonly nicknamed the Pearl of the Pacific Northwest.

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